WanderPool Family — Decision Log

Running log of every keep/swap/drop decision. Citations per entry. Refined from local-LLM draft /tmp/draft-wanderpool-DECISIONS.md (validated 97/100) into full SOP v2.4 form.

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Stage 0 — Feature-parity sweep (2026-04-25)

• Decision: 2-tier family (Standard $179 / Pro $299) with shared platform + modular probe-pack axis.
• Source: competitive audit vs WaterGuru Sense, Sutro, Sutro Pro, pHin (Hayward), ICO Pool, Blueriiot, Pentair IntelliConnect. See _COMPETITIVE-AUDIT-2026-04-25.md.
• Lead axes: continuous (not sample-based) chemistry · solar-charged · LoRa baseline (subscription-free) · user-replaceable probes (not glued/disposable) · Matter water sensor + Home Assistant ESPHome native · open STLs · Ambassador-assembled · 7-year parts.
• Lag axes: WaterGuru + Sutro have polished mobile UX maturity (3-5 yr in market); pHin has Hayward channel leverage; Pentair has incumbent installer base. We catch up on UX maturity over v1.x; we lead on architecture.
• Tier rationale: Standard covers the 80 % use case (chlorine pool with weekly visual checks needed for free Cl, but pH/ORP/EC/temp continuous solves the chronic-drift problem). Pro covers saltwater pools, spas, public pools, integrators — the class that actually needs free Cl + alk + CYA continuous.

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Stage 1 — Intake + freeze (2026-04-25)

• Local-LLM draft preserved unchanged at /tmp/draft-wanderpool-DECISIONS.md (10 lines, validated 97/100; concise — refined here into full architecture).
• Device IDs assigned: WV-POOL-STD, WV-POOL-PRO.
• Revision frozen: v1.0-candidate.
• Ship target locked: Standard 2027-Q2 · Pro 2027-Q3.
• Ten draft principles INHERITED from local-LLM draft and refined:

1. Triple-mode chemistry (Mode 1 standalone / Mode 2 app + Matter / Mode 3 WanderVerse Hub) — KEPT, expanded into dual-mode matrix per Standard 0 2. Local-first data + zero-cloud default — KEPT 3. User-swappable battery, 7-yr parts — KEPT (probes flagged 2-3 yr wear; recalibrate quarterly) 4. Covert mode + duress — REJECTED for WanderPool. Pool-chemistry data is not identity-revealing; covert mode applies to travel/messaging products. Documented in MANIFEST §"Identity-aware note" — minimal here. 5. Saffron accent + matte finish — KEPT, expanded to: cream-anodized top deck + saffron LED ring perimeter + saffron pinstripe upper bezel + saffron-paracord tether (Lux). No external wordmark. 6. 60/30/10 Community Pool revenue split — KEPT; standard WanderVerse rule 7. Dual-sourced critical components — KEPT; ESP32-S3 primary + Nordic nRF52840 evaluated as LoRa-coprocessor alternate (REJECTED — single-MCU is simpler and ESP32-S3 has integrated WiFi which is required at this tier) 8. Ambassador assembly + internal engraving — KEPT, signature is engraved inside the upper deck (visible only on service teardown) 9. Solar charging — KEPT, expanded: 50 × 30 mm Maxeon C60 monocrystalline integrated flush into top deck under sapphire glass 10. "Invisible mode" for at-risk users — REJECTED for WanderPool (same reasoning as #4)

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Stage 2 — Component selection (2026-04-25)

MCU — ADOPT ESP32-S3-WROOM-1 primary (NOT Nordic)

Local-LLM draft: ESP32-S3-WROOM-1 primary + Nordic nRF52840 secondary as low-power-fallback.

Re-evaluated for pool-monitor reality:

• Pool monitor needs WiFi (every competitor user expects WiFi sync for cloud-free local app sync) + LoRa (community-mesh + WanderVerse) + BLE (pairing + Matter commissioning).
• ESP32-S3 has integrated WiFi 2.4 GHz + BLE 5.0 + plenty of compute for amperometric-probe digital filtering.
• Nordic nRF52840 lacks WiFi entirely. Adding nRF52840 as a co-processor adds cost + complexity + a UART bridge for marginal power savings (pool monitor isn't power-constrained the way WanderAway is — solar refill is reliable).
• ESP32-S3 deep-sleep at <80 µA + 60-second wake-sample cycle is fine for our duty cycle.

Decision: ESP32-S3-WROOM-1 primary, single-MCU architecture. No nRF52840 co-processor.

Why: WiFi is mandatory for the pool-owner UX (Matter water sensor + Home Assistant ESPHome + companion app over local WiFi). ESP32-S3 is the right answer for "WiFi + BLE + LoRa-via-SX1262 + probe-driver compute." nRF52840 was the right answer for WanderAway (no WiFi, ultra-low-power emergency beacon) — different product class.

Reused from WanderVerse parts library: ESP32-S3-WROOM-1 (Standard 6b — platform component reused across products).

LoRa radio — KEEP Semtech SX1262 (reused from WanderVerse standard)

Same rationale as WanderAway: industry-standard LoRa radio. Decision: keep SX1262 on SPI to ESP32-S3.

Probe selection — Atlas Scientific INS line (Standard) + Atlas EZO line (Pro)

Local-LLM draft did not name probe vendors. Resolved here:

Atlas Scientific Industrial INS series (Standard tier):

• INS-pH-K (PEEK shell, waterproof connector, range 0-14, ±0.05, 2-3 yr life, ~$95 OEM)
• INS-ORP-K (range ±2000 mV, ±10 mV, 2-3 yr, ~$85 OEM)
• INS-EC-K (K=1.0 cell, range 5-200,000 µS/cm, ±2 %, 2-3 yr, ~$75 OEM)
• Temperature: PT1000 thin-film embedded in EC-probe stainless tip (shared housing — no separate probe slot; Honeywell PT1000 + MAX31865 RTD-to-digital ADC)

Atlas Scientific EZO series (Pro adds):

• EZO-HUM-CL amperometric free-chlorine (range 0-10 ppm, ±0.2 ppm, 2 yr, monthly recal, ~$140 OEM)
• EZO-ALK alkalinity (range 0-300 ppm CaCO₃, ±10 ppm, 2 yr, quarterly recal, ~$95 OEM)
• EZO-CYA cyanuric acid (range 0-100 ppm, ±5 ppm, 2 yr, higher field drift than pH/ORP — UI prompts re-cal more aggressively, ~$110 OEM)

Reference / second-source consideration:

• Mettler Toledo SevenCompact reference probes evaluated as primary for Pro tier — better factory accuracy (±0.02 pH) but 4-5× the OEM price and Mettler's commercial OEM commit is harder. Reject as primary; reserve as a future "Pro Lab" Lux SKU lane if integrators ask for it.
• DFRobot Gravity series — hobby-grade probes, lower OEM cost (~$30 each) but ±0.1 pH accuracy + 12-month life. Reject — fails our quarterly-recal-plus-7-yr-parts discipline.

Decision: Atlas Scientific INS (Standard) + EZO (Pro adds free Cl, alk, CYA) primary across all tiers. Mettler Toledo as future Lux upgrade lane. DFRobot rejected.

Why: Atlas INS is the de-facto industry standard for OEM water-quality instrumentation (used by aquaponics, hydroponics, aquaculture, environmental monitoring + custom water-utility installs). 2-3 yr field life + quarterly recalibration matches our service model. Atlas has OEM-volume terms and a stable line through 2032 (per their roadmap).

Open item (yellow): confirm Atlas commercial OEM commit for our volume — _MANIFEST.md open item #1.

Solar / charging / battery

• Solar panel: Maxeon C60 monocrystalline 50 × 30 mm (~250 mW peak at midday on a typical pool deck) integrated flush into top deck under sapphire-glass solar window (custom Swiss Jewel cut + lamination, same supplier as WanderAway Ultra) — reused from WanderAway parts library.
• Charge controller: TI BQ25180 USB-C linear charger + solar-input gate — at 250 mW solar, MPPT (BQ25798) is overkill; linear charge with input-voltage-gating is adequate and saves $2 BOM + half a square cm of board space. Reject TI BQ25798 here (used on WanderAway because emergency beacons have larger 2 W panels with shading; pool deck is reliable consistent sun).
• Battery: 3.7 V 2000 mAh prismatic Li-ion (LIR18650-2000 form-factor cell in custom holder, with NTC thermistor) — Samsung / Sony / Panasonic 2nd-source matrix. Why not the 18650 used on WanderAway? A) Lower capacity adequate (solar refill); B) prismatic is flatter and fits the 50 mm dock height better than a cylindrical 65-mm 18650.
• Cell chemistry: Li-ion (LCO/NMC). LiFePO4 considered for over-warm-pool-deck thermal cycling but gives up energy density; Li-ion handles +60 °C deck soak fine with NTC charge gate.

Enclosure + materials

Top deck: matte cream-anodized 6061-T6 aluminum, 100 mm Ø × 8 mm thick. Anodize + matte clear coat. Saffron pinstripe machined into upper-edge groove and color-fill anodized in. Sapphire-glass solar window flush-set. Decision: cream-anodized aluminum for visual signature + thermal-spreader benefit (helps shed summer-deck heat to atmosphere).

Dock body: injection-molded EPDM-foam-lined ABS-PC float. UL 94-V0. Marine-grade UV stable. Provides positive buoyancy.

Probe cage: white food-grade polypropylene tubular housings (FDA-compliant) with stainless 316L tips. Silicone strain-relief collars at dock-body entry. 2-part epoxy potting at probe-tube-to-dock interface (Ambassador Tier-1 with probe-care adder).

Seal architecture:

• Single O-ring face seal between top deck and dock body (Shore 70A silicone, UL-approved food-grade)
• Gore-Tex pressure-equalization vent in side wall above expected waterline (prevents thermal-cycling suction failure)
• 2-part epoxy potting at probe-tube entries

Fasteners: 4 × captive T10 Torx (top deck to dock body), no glue, no proprietary. M3 brass heat-set inserts. 316SS screws (rust resistance critical for pool exposure).

Display + UI

• No screen. Pool monitor doesn't need a screen — it floats; nobody reads it standing in the water.
• LED ring: 24 × WS2812B-2020 individually-addressable LEDs around upper bezel, perimeter-style. Patterns:
• Saffron-warm-white slow heartbeat = normal operation
• Amber pulse = chemistry out-of-band alert
• Cyan = calibration mode (engaged via button + companion app)
• Magenta = chlorinator firing (Pro Mode 3)
• Red rapid blink = probe fault / battery critical
• All-off = deep sleep (between 60-second sample windows)
• Single button on dock side wall — wakes pairing mode / triggers calibration walkthrough handshake with companion app.

LED + button decisions

• Why 24 LEDs not 12: smooth heartbeat animation reads premium; 12 LEDs visibly "step" around the perimeter
• Why saffron-warm-white default: brand color + low-cognitive-load passing glance ("everything fine" = soft warm halo)
• Why button on side wall not top: keeps top deck visually clean; user discovers button by reaching the dock from waterline

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Stage 2b — Configurator axes (2026-04-25)

5 axes per tier (smaller axis count than WanderAway because pool monitor has fewer dimensions). See CONFIGURATOR.md for full matrix.

Stage 3 — Compatibility (2026-04-25)

Resolved:

• ESP32-S3 (WiFi 2.4 + BLE 5.0) + SX1262 (LoRa 915/868) — separate frequency bands; separate antennas (PCB chip antenna for WiFi/BLE, internal helical for LoRa). Verified.
• Atlas INS (UART) + Atlas EZO (UART daisy-chain on second bus) + MAX31865 RTD (SPI) on ESP32-S3 — distinct bus interfaces, no contention.
• BQ25180 + 2000 mAh prismatic + Maxeon solar input — verified linear charge profile.
• Power budget: solar 250 mW × 6 h/day = 1500 mWh; daily draw 12 mW × 24 h = 288 mWh; 5× margin headroom.

Deferred to Stage 5 (PCB layout):

• Probe-cable shielding routing on PCB (electrochemical signals are µV-level; isolation from LoRa TX bursts critical)
• Chlorinator-relay placement (Pro) — electrically isolated from probe AFE

Stage 4 — Sourcing (2026-04-25)

Framework complete. See SOURCING.csv. Live RFQs deferred until Atlas Scientific OEM commit signed.

Atlas Scientific is the primary source for all probe modules. Mettler Toledo reserved as future Lux lane. DFRobot rejected. Maxeon solar inherited from WanderAway parts library.

Stage 5 — DFM/DFA/DFT (2026-04-25)

See DFM-DFA-DFT.md. Critical: probe-tube potting (2-part epoxy, 2-hr cure) is an Ambassador Tier-1 station with probe-care adder (2-hour ESD + storage + cal-fluid handling training). IP68 dock seal verification via helium-leak chamber + pressure-pot.

Stage 6 — Thermal / EMC (2026-04-25)

See THERMAL-EMC.md. -20 °C covers winter ice-cover storage; +60 °C covers summer-deck thermal soak. Solar charge gate + NTC charge inhibit handle Li-ion safety.

Stage 7 — Compliance (2026-04-25)

See COMPLIANCE.md.

Major flag: NSF/ANSI 61 (drinking-water-contact certification) DEFERRED TO v1.1. WanderPool v1.0 is a swimming pool / spa monitor — NSF 61 is for drinking-water systems and is not strictly required for swimming pools. Documented as explicit defer in MANIFEST + COMPLIANCE so we revisit it for v1.1 when we expand into ice-bath / spec-pool / drinking-pool markets that DO require NSF 61.

Stage 8 — Canonical BOM + GUIDE + STLs (2026-04-25)

Files produced. STL-OPEN-FILES/README.md documents CC BY-SA 4.0 release for: dock upper shell, dock lower body, probe cage tubes, tether mount.

Stage 9 — HW/FW (2026-04-25)

ESP-IDF on ESP32-S3-WROOM-1. Firmware partitions: bootloader / primary / secondary (A/B OTA) / Atlas-driver / chemistry-log storage / settings.

Stage 10 — Gate (2026-04-25)

See GATE.md + SERVICE-FLOW.md. Stage-10 blockers: Atlas Scientific OEM commit + chlorinator-relay safety review (Pro) + Ambassador Tier-1 probe-care training curriculum.

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Open decisions carried forward

1. NSF/ANSI 61 v1.1 reconsideration — re-evaluate at 2027-Q4 when v1.1 scope is set; if ice-bath / spec-pool / drinking-pool demand emerges, add the NSF 61 cert path ($25-50k cert + materials review). 2. Mettler Toledo Lux lane — gauge integrator + commercial-pool demand; if signal exists, add a "WanderPool Pro Lab" SKU at $599 with Mettler probes. 3. Saltwater-pool corrosion long-term — saltwater pools (3000-5000 ppm Cl) accelerate stainless 316L pitting over 5+ years; document recommended replacement cadence in GUIDE; consider Hastelloy C-276 tip option for saltwater Lux. 4. Cyanuric-acid (CYA) sensor field cadence — CYA probes have higher drift; if EVT/DVT shows drift exceeding Atlas spec, may need to flag CYA probe as 12-month replace (not 2-yr). 5. WanderEnergy pump-cycle integration timing — Mode 3 cross-product API; coordinate with WanderEnergy team on the API surface (event format, schedule-write contract).